class Maybe {
  static of (value) {
    return new MayBe(value)
  }
  constructor (value) {
    this._value = value
  }
  map (fn) {
    return this.isNothing() ? MayBe.of(null) : MayBe.of(fn(this._value))
  }
  isNothing () { // 判断value是否为空
    return this._value === null || this._value === undefined
  }
}
class Container {
  static of (value) {
    return new Container(value)
  }
  constructor (value) {
    this._value = value
  }
  map (fn) {
    
  }
}

module.exports = { 
  Maybe,
  Container
}